XMM-Newton observations of open clusters Original Research Article

We present observations of stellar clusters obtained with XMM-Newton as part of the Guaranteed Time program. We have obtained EPIC observations of the open clusters Praesepe, a Per, o Ori and Hyades and of the Taurus-Auriga star-forming region. The results of the analysis are presented and discussed, with emphasis on the imaging data. In all clusters a large number of new X-ray sources with no known catalogued optical counterpart has been detected. In σ Ori three X-ray sources coincide with very-low mass members of the cluster, including a brown dwarf candidate. The Praesepe observation does not show the discrepancy with the Hyades found by ROSAT, supporting the suggestion that this cluster may be formed by two merged clusters of different ages.